Leyla Yunus was given an eight-and-a-half year sentence while her husband Arif was jailed for seven years on charges that include fraud and tax evasion, their lawyer said.
Lawyer Ramiz Mamedov insisted that the couple -- both of whom are said to be suffering ill health -- were innocent and the trial had failed to provide evidence of any crimes.
"The charges of fraud, tax evasion and embezzlement were not proved at the trial," Mamedov said.
Rights activists slammed the court's decision as an attempt by Azerbaijan's iron-fisted authorities to block the couple's human rights work.
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Arrested last year on suspicion of spying for arch-foe Armenia, the couple also face treason charges in a separate case.
Leyla Yunus, 59, heads one of Azerbaijan's leading rights groups, the Institute for Peace and Democracy, in the capital Baku.
She has won several international awards for her work, and has teamed up with Armenian activists to urge reconciliation between the two countries, locked in a decades-long conflict over the disputed Nagorny Karabakh region.
Her 60-year-old husband suffers from high blood pressure that saw him collapse at least once during the month-long trial.
"My parents are sentenced to death today," the couple's daughter Dinara, who lives in the Netherlands, wrote on Twitter after the court announced its decision.
Dissent in tightly-controlled Azerbaijan is often met with a tough government response.
Rights groups say the government of the oil-rich ex-Soviet republic has stepped up pressure on opponents since President Ilham Aliyev's election for a third term in 2013.
"The Azerbaijani authorities should now do the right thing, have the convictions and sentences set aside, and turn a page on the appalling crackdown against human rights defenders, of which the Yunuses are victims.